1. Field of the Invention
The present invention relates to an apparatus for operating and controlling a textile machine designed to process a roving in order to form it into a yarn made from a continuous sequence of portions, each portion having predetermined count and/or twist characteristics.
2. Description of Related Art
In particular, the present invention relates to an operating and control apparatus designed to be associated particularly, but not solely, with a textile machine such as a ring spinning machine.
In the modern textile industry, there is an increasing trend towards the production of high-value textiles, frequently characterized by unusual aesthetic qualities which distinguish them from ordinary products.
In particular, it is known that the count or twist characteristics of a yarn can affect the aesthetic qualities of the textile made from the yarn.
The variation of the count of a yarn, in other words the variation of its nominal diameter along its length, gives rise to a thickening or thinning of the textile made from the yarn, giving it pleasing aesthetic qualities.
In this case, the yarn is called “slub yarn”, and the corresponding process is called “slubbing”. Alternatively, with certain differences taken into consideration, the yarn and the process are called “multicount”.
Similarly, a variation in the twist of the yarn is related to its capacity to absorb colour. In this case also, if this characteristic is exploited skilfully, it is possible to produce textiles having unusual chromatic characteristics which, as is done increasingly frequently, make the textile into a high-value product. In this case, the process and the corresponding yarn are called “multitwist”.
It is also possible to vary the count and the twist simultaneously. In this case, the process and the corresponding yarn are called “multicount-multitwist”.
Generally, the yarn is processed in such a way that it acquires the desired count and/or twist characteristics in a ring spinning machine, by passing through specially designed drawing and twisting devices in which the count or the twist of the yarn is varied by suitably adjusting the speed of the drawing rollers or the spindles.
An example of a textile machine based on the aforesaid principle is described in GB-A-2034764.
There is also a known way of generating appropriate reference signals which, when suitably interpreted by dedicated devices of the textile machine, adjust the speed of the driving means in order to generate a yarn in which the variation of the count or of the twist corresponds to the values of a specified function.
An example of an embodiment as above is described in EP 669414.
However, it is frequently the case that processes designed to produce yarns having specific count and/or twist characteristics as specified above form only part of the actual production process of a textile business, most of whose output consists of basic yarns having specified count and/or twist characteristics throughout their length.
This makes it necessary to have machines of the conventional type and modern machines, capable of carrying out multicount, multitwist or multicount-multitwist processing, available simultaneously. Alternatively, if modem textile machines are used exclusively, the costs incurred by programming them in order to use them as conventional machines have to be met.
There is thus a requirement, which has not yet been met, for the use of modern textile machines in a simple and efficient way both for carrying out stubbing, multicount, multitwist or multicount-multitwist processes and for carrying out conventional spinning processes in which the count and twist remain constant along the length of the yarn which is produced.